Atherosclerosis results when fat, cholesterol, and calcium deposits, all referred to as plaque, accumulate inside the arteries. Arteries are vital in that they carry oxygen-rich blood throughout the body. As these deposits build in the arteries, the supply of this blood is diminished, and can cause heart attacks, strokes, or death.
Particulate matter may be one of the contributing factors to these detrimental health effects. This substance is released from the burning of gasoline and from the combustion of fuels within power plants. The researchers discovered that the presence of fine particulate matter (PM2.5) was linked to the buildup of plaque within the inner two layers of the common carotid artery. The carotid artery supplies blood to the front portion of the brain, as well as the head, neck, face, and spinal cord. In contrast, the researchers also found that lower levels of particulate matter were associated with a slower thickening of the arteries.
In order to find these results, the researchers obtained data from the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air), which followed 5362 people between the ages of 45 and 84 without known heart problems in order to find a link between air pollution and cardiovascular disease. MESA Air is a ten-year study and is funded by the EPA.
The scientists adjusted for personal factors such as smoking. The people examined in the study live in six major metropolitan areas in the United States. MESA Air has set up data collection with fixed site pollution monitoring equipment, air samplers, home outdoor and indoor monitoring equipment, and from personal sampling. Air pollution levels were measured at each person’s house and were matched with two ultrasound measurements of the blood vessels. Each reading was separated by a three-year gap. Those exposed to higher levels of particulate matter within the same city experienced faster plaque buildup, potentially increasing the risk for strokes and heart attacks. There are limitations to this study, however, including outside factors other than particulate matter that may be linked to the plaque buildup.
Despite its potential limitations, this study highlights the need for strong environmental legislation due to its significance in predicting long-term harmful human health effects.
Photo of Beijing smog courtesy of Bobak Ha'Eri via Wikimedia Commons.